Power supply



FIG. 1 is a perspective view of a power supply showing my new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a bottom plan view thereof;

FIG. 6 is a right side elevation view thereof; and,

FIG. 7 is a left side elevation view thereof.

The broken lines shown represent unclaimed subject matter and form no part of the claimed design. 

The ornamental design for a power supply, as shown and described. 